The Cancer Imaging Program has developed a contract supported infrastructure to support Phase I (Safety) and Phase II (Preliminary Efficacy) clinical trials of promising imaging agents and methodologies. These clinical trials are used to evaluate the safety and diagnostic imaging capabilities of promising imaging probes, ligands, radiopharmaceuticals, and contrast agents that are of interest to NCI. The role of these imaging tests in various aspects of cancer management [unreadable] i.e. diagnosis, staging, assessment of response to treatment is evaluated. The Safety and Preliminary Efficacy Imaging Clinical Trials contracts create an infrastructure to evaluate molecularly-targeted imaging agents used to assess therapeutic anticancer agents on their molecular targets and determine clinically relevant correlates. The major emphasis is on imaging agents which are found to be safe and provide important structural, metabolic, or molecular imaging data which are important and useful in the management of patients with cancer. These contracts support the ability to implement correlative studies validating the localization of the investigational imaging agents on their molecular target in tumors. Imaging agents may originate from investigators not affiliated with clinical sites. There have been two issuances of a Request for Proposals and four (4) contracts have been awarded. The size of each trial varies depending on consultation with the FDA for each specific agent. The typical size for each Safety trial is approximately 10 patients. The typical size for each Preliminary Clinical Efficacy trial is estimated to be 25-50 patients